An increasing number of biological studies reveal the strong interaction between different cellular compartments in vivo. To accurately study and model these phenomena in vitro, traditional cell-biology platforms have been used on the periphery of their designed use. Microfluidic and microfabricated platforms are a natural fit for these applications as they provide unique capabilities to controllably place different cellular compartments in two-dimensional (2D) or three-dimensional (3D) matrices. Two main fluidic approaches have been demonstrated to achieve this task. The first fluidic approach segregates liquid compartments by providing a highly resistive fluidic path, such as a diffusion channel or a membrane, thereby allowing a user to load in contiguous chambers multiple cell types. This approach has proven to enable multi-culture of up to 5 cell types, as well as, increase the sensitivity as compared to traditional transwell dishes. The second fluidic approach leverages laminar (i.e. not turbulent) flow properties to fluidically pattern the different cell types in a channel. Laminar flow is employed by flowing two streams, side-by-side, within a channel in order to pattern cells, particles, and treatments. Laminar flow may also be used for developing gradients, where one chemical diffuses laterally from one stream into the other. It can be appreciated that this method maximizes the efficiency of the soluble factor signaling as the exchange of soluble factors is highest, while the volume per cell ratio is low.
Currently, there are no methods for reproducibly controlling laminar flow in a practical way. Hence, this fluidic approach remains seriously underutilized. Further, traditional microfluidic methods for reproducibly controlling laminar flow are not readily amendable to biological studies due to limitations such as connectivity problems (tubing, dead volumes, air bubbles, etc.). Recently, microdevices have been developed to alleviate these issues by integrating seamlessly with traditional equipment from the biology lab. These microdevices utilize surface tension-driven pumping or gravity pumping with a simple micropipette. In cell-based applications, the loading volumes are finite, usually from 1 to 10 μL, and the process is sequential. Therefore, flow patterning methods are more difficult to achieve as the flow varies over time. In particular, since the flow is limited in time, any differences in pressures occurring at the end of the motion will induce large changes in patterning. Further, the use syringe pumps to achieve laminar flow requires exact timing to achieve desirable results. This is due to the need to synchronize flows to avoid causing one stream to flow into the region of another, thereby disturbing the pattern.
Therefore, it is a primary object and feature of the present invention to provide a device for controlled laminar flow patterning of at least one sample fluid in a channel of a microfluidic device.
It is a further object and feature of the present invention to provide a method of laminar flow patterning of at least one sample fluid in a main channel in a microfluidic device.
It is a still further object and feature of the present invention to provide a device and a method of laminar flow patterning of at least one sample fluid in a main channel in a microfluidic device that is simple and inexpensive to implement.
In accordance with the present invention, a device is provided for controlled laminar flow patterning of at least one sample fluid. The device includes a body defining a channel network. The channel network includes a main channel extending along a longitudinal axis and having a first end and a second end defining an output port. A first input channel has an output end communicating with the first end of the main channel and an input end communicating with a first input port. The first input channel has a fluidic resistance. The channel network further includes a fluidic capacitor and a first buffering channel. The first buffering channel has a first end communicating with the first input channel and the first input port and a second end communicating with the fluidic capacitor. The first buffering channel has a fluidic resistance less than the fluidic resistance of the first input channel.
The channel network in the body of the device further includes a second input channel having an output end communicating with the first end of the main channel and an input end communicating with either the first input port or, alternatively, with a second input port. The second input channel having fluidic resistance. In the alternate embodiment, a second buffering channel has a first end communicating with the second input channel and the second input port and a second end communicating with the fluidic capacitor. The second buffering channel has a fluidic resistance less than the fluidic resistance of the second input channel.
A buffering fluid may be provided within the channel network and the at least one sample fluid may include a first sample fluid and a second sample fluid. It is intended for the fluidic capacitor to urge laminar flow of the first and second sample fluids in the main channel in response to the asynchronous depositing of the first sample fluid in the first input port and the second sample fluid in the second input port. Further, it is contemplated for the first and second input channels to have cross sectional areas and for the first and second buffering channels to have cross sectional areas. The cross sectional area of the first buffering channel is greater than the cross sectional area of the first input channel and the cross sectional area of the second buffering channel is greater than the cross sectional area of the second input channel. Similarly, the fluid capacitor, the first input port and the second input port have cross sectional areas. The cross sectional area of the fluid capacitor is greater than the cross sectional areas of the first and second input ports.
In accordance with a further aspect of the present invention, a method is provided of laminar flow patterning of at least one sample fluid in a main channel in a microfluidic device. The method includes the step of providing a first input channel in the microfluidic device. The first input channel has an output end communicating with the first end of the main channel and an input end communicating with a first input port. A buffer fluid is deposited in the main channel and in the first input channel. A first sample fluid is deposited in the first input port and a first pressure is generated in response to the depositing of the first sample fluid in the first input port. The first pressure causes laminar flow of the first sample fluid in the main channel.
A fluidic capacitor may be provided in communication with the first input channel and the buffer fluid being received in the fluidic capacitor. The buffer fluid in the fluidic capacitor has a surface tension pressure and the pressure causing laminar flow of the first sample fluid in the main channel is the surface tension pressure of the buffer fluid in the fluidic capacitor.
The method may include the additional step of providing a second input channel in the microfluidic device. The second input channel has an output end communicating with the first end of the main channel and an input end communicating with a second input port. The buffer fluid is deposited in the second input channel and a second sample fluid is deposited in the second input port. A second pressure is generated in response to the depositing of the second sample fluid in the second input port. The second pressure combines with the first pressure to provide a total pressure for causing laminar flow of the first and second sample fluids in the main channel along corresponding flow paths. In addition, the flow paths of the first and second sample fluids have corresponding widths. The widths of the flow paths are proportional to the fluidic resistances of the flow paths.
The method may also include the additional step of providing a fluidic capacitor in communication with the first and second input channels. The buffer fluid is received in the fluidic capacitor. The buffer fluid in the fluidic capacitor has a surface tension pressure and the total pressure causing laminar flow of the first and second sample fluids in the main channel is the surface tension pressure of the buffer fluid in the fluidic capacitor.
A second input channel may be provided in the microfluidic device. The second input channel has an output end communicating with the first end of the main channel and an input end communicating with a first input port. The buffer fluid is deposited in the second input channel. A first portion of the first sample fluid flows along a first flow path in the main channel and a second portion of the first sample fluid flows along a second flow path in the main channel.
In accordance with a still further aspect of the present invention, a method is provided of laminar flow patterning of at least one sample fluid in a flow channel in a microfluidic device. The method includes the step of providing a first input flow path between a first input port and the flow channel. The first flow path has a fluidic resistance. A first sample fluid is deposited in the first input port and a first pressure in response to the depositing of the first sample fluid in the first input port. The first pressure causes laminar flow of the first sample fluid in the fluid channel.
A fluidic capacitor may be provided in communication with the first input flow path and the first input port through a first buffering flow path. The first buffering flow path has a fluidic resistance less than the fluidic resistance of the first input flow path. The step of generating the first pressure includes the additional step of depositing a buffer fluid in the fluidic capacitor. The buffer fluid has a surface tension pressure and the pressure causing laminar flow of the first sample fluid in the flow channel is the surface tension pressure of the buffer fluid in the fluidic capacitor.
A second input flow path is provided between a second input port and the flow channel. The second flow path has a fluidic resistance. A second sample fluid is deposited in the second input port and a second pressure is generated in response to the depositing of the second sample fluid in the second input port. The second pressure combines with the first pressure to provide a total pressure for causing laminar flow of the first and second sample fluids in the flow channel along corresponding flow paths. The flow paths of the first and second sample fluids within the flow channel have corresponding widths. The widths of the flow paths in the flow channel are proportional to the fluidic resistances of the flow paths.
Alternatively, the second input flow path may communicates with flow channel and the first input port. As such, the first pressure causes laminar flow of a first portion of the first sample fluid along a first flow path in the flow channel and laminar flow of a second portion of the first sample fluid along a second flow path in the flow channel.